/**

Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016.  All rights reserved.

Contact:
     SYSTAP, LLC DBA Blazegraph
     2501 Calvert ST NW #106
     Washington, DC 20008
     licenses@blazegraph.com

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
/*
 * Created on Nov 1, 2015.
 */

package com.bigdata.rdf.sparql.ast.hints;

import com.bigdata.rdf.sparql.ast.ASTBase;
import com.bigdata.rdf.sparql.ast.PropertyPathNode;
import com.bigdata.rdf.sparql.ast.QueryHints;
import com.bigdata.rdf.sparql.ast.QueryRoot;
import com.bigdata.rdf.sparql.ast.eval.AST2BOpContext;

/**
 * Query hint to enable users choose the gearing used for evaluating
 * recursive property paths. Generally speaking, the problem with recursive
 * property path queries is that it is inherently hard to choose the gearing.
 * This hint allows the user to take control over the gearing.
 * 
 * @author <a href="mailto:ms@blazegraph.com">Michael Schmidt</a>
 */
final class GearingHint extends AbstractStringQueryHint {

    protected GearingHint() {

        super(QueryHints.GEARING, null/* default */);

    }

    @Override
    public void handle(final AST2BOpContext context,
            final QueryRoot queryRoot,
            final QueryHintScope scope, final ASTBase op, final String value) {

       
       switch (scope) {
       case Prior:
       {
          if (op instanceof PropertyPathNode) {
             _setQueryHint(context, scope, op, getName(), value);          
             return;
          }
          
          // fall through
       }
       default:
          break;
       }

       // query hint does not make sense in other situations
       throw new QueryHintException(scope, op, getName(), value);


    }

}
